One of the most common techniques for dispensing carbonated beverages is to mix a relatively small quantity of concentrated beverage syrup with a relatively large quantity of carbonated water immediately prior to serving the beverage. The syrup and carbonated water are drawn from their respective containers through tubing into a cooler where the fluids are separately cooled. Failure to adequately cool the liquids is distressing to the consumer. After the fluids are separately cooled in the cooler, they are mixed at a tap for delivery to the container or glass provided to the consumer.
A commonly used cooler because of its simplicity and low cost is constructed of a thermally insulated box in which is placed flakes or cubes of ice. The ice rests on a cold plate provided at the bottom of the box. The cold plate is commonly formed of a cast aluminum block which encases a plurality of serpentine shaped coils. The coils are formed of tubing through which the syrup and carbonated water pass. Heat is conducted from the syrup and carbonated water passing through the coils, through the plate and to the ice. Because a much larger quantity of carbonated water relative to syrup is required for a typical beverage, there are usually at least three coils for cooling carbonated water for each coil carrying a syrup. However, a plurality of syrup cooling coils are usually provided so that a number of beverages can be served, with the carbonated water being used for all the beverages.
A severe problem with this type of cooler is the occurrence of "bridging" of the ice. The inlets for the syrup and carbonated water are all generally provided at one end of the cold plate and the outlets at the opposite end of the cold plate. This fact, coupled with the serpentine nature of the coils within the cold plate, provides for a significant thermal gradient in the cold plate. This thermal gradient causes the ice to melt faster near the inlet of the coils, melting the ice in contact with that particular area of the cold plate. The liquid is then drained from the cooler through a drain hole and the ice thus bridges over that portion of the cold plate, significantly diminishing the cooling of the syrup and carbonated water. A need therefore exists for a cooler which minimizes this bridging problem, yet remains economical.